On Fri, 22 Dec 2023 14:50:16 GMT, Joachim Kern <jk...@openjdk.org> wrote:
>> On AIX, repeated calls to dlopen referring to the same shared library may >> result in different, unique dl handles to be returned from libc. In that it >> differs from typical libc implementations that cache dl handles. >> >> This causes problems in the JVM with code that assumes equality of handles. >> One such problem is in the JVMTI agent handler. That problem was fixed with >> a local fix to said handler >> ([JDK-8315706](https://bugs.openjdk.org/browse/JDK-8315706)). However, this >> fix causes follow-up problems since it assumes that the file name passed to >> `os::dll_load()` is the file that has been opened. It prevents efficient, >> os_aix.cpp-local workarounds for other AIX issues like the *.so/*.a duality. >> See [JDK-8320005](https://bugs.openjdk.org/browse/JDK-8320005). As such, it >> is a hack that causes other, more uglier hacks to follow (see discussion of >> https://github.com/openjdk/jdk/pull/16604). >> >> We propose a different, cleaner way of handling this: >> >> - Handle this entirely inside the AIX versions of os::dll_load and >> os::dll_unload. >> - Cache dl handles; repeated opening of a library should return the cached >> handle. >> - Increase handle-local ref counter on open, Decrease it on close >> - Make sure calls to os::dll_load are matched to os::dll_unload (See >> [JDK-8320830](https://bugs.openjdk.org/browse/JDK-8320830)). >> >> This way we mimic dl handle equality as it is implemented on other >> platforms, and this works for all callers of os::dll_load. > > Joachim Kern has updated the pull request incrementally with one additional > commit since the last revision: > > additional fix of sideeffect reported in JDK-8322691 src/hotspot/os/aix/porting_aix.cpp line 1071: > 1069: if (max_handletable == 0) { > 1070: // First time we allocate memory for 128 Entries > 1071: char* ptmp = (char*)::malloc(128 * sizeof(struct > handletableentry)); No need for malloc. You can start with realloc, since realloc(NULL, ...) is malloc. static handletablentry* tab = nullptr; static unsigned max_handles = 0; ... if (need more handles) unsigned new_max = MAX2(max_handles * 2, init_num_handles); handleentry* new_tab = ::realloc(p_handletable, sizeof(handleentry) * new_max); if (new_tab != nullptr) { max_handles = new_max; tab= new_tab; } ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16920#discussion_r1435139923
